A South Korean security expert says North Korea probably has enough nuclear material for somewhere between 22 and 45 nuclear weapons.

Lee Sang-hyun of the Sejong Institute says North Korea is currently presumed to possess around 280 kilograms of highly enriched uranium and 52 kilograms of plutonium at the moment. His prediction is part of a report presented at a Seoul security conference Thursday.

Unlike plutonium, highly enriched uranium can be secretly produced at very small-scale facilities, making it very difficult to track. 

Lee said the North's plutonium stockpile is expected to increase six kilograms each year, while uranium may increase by as much as 80 kilograms.